A security issue affects these releases of Ubuntu and its derivatives:

- Ubuntu 11.10
- Ubuntu 11.04
- Ubuntu 10.10
- Ubuntu 10.04 LTS

Summary:

Tomcat could be made to crash or expose sensitive information over the
network.

Software Description:
- tomcat6: Servlet and JSP engine

Details:

It was discovered that Tomcat incorrectly implemented HTTP DIGEST
authentication. An attacker could use this flaw to perform a variety of
authentication attacks. (CVE-2011-1184)

Polina Genova discovered that Tomcat incorrectly created log entries with
passwords when encountering errors during JMX user creation. A local
attacker could possibly use this flaw to obtain sensitive information. This
issue only affected Ubuntu 10.04 LTS, 10.10 and 11.04. (CVE-2011-2204)

It was discovered that Tomcat incorrectly validated certain request
attributes when sendfile is enabled. A local attacker could bypass intended
restrictions, or cause the JVM to crash, resulting in a denial of service.
(CVE-2011-2526)

It was discovered that Tomcat incorrectly handled certain AJP requests. A
remote attacker could use this flaw to spoof requests, bypass
authentication, and obtain sensitive information. This issue only affected
Ubuntu 10.04 LTS, 10.10 and 11.04. (CVE-2011-3190)

Update instructions:

The problem can be corrected by updating your system to the following
package versions:

Ubuntu 11.10:
libtomcat6-java 6.0.32-5ubuntu1.1

Ubuntu 11.04:
libtomcat6-java 6.0.28-10ubuntu2.2

Ubuntu 10.10:
libtomcat6-java 6.0.28-2ubuntu1.5

Ubuntu 10.04 LTS:
libtomcat6-java 6.0.24-2ubuntu1.9

In general, a standard system update will make all the necessary changes.